Encapsulated agglomeration of microcapsules and method for the preparation thereof

ABSTRACT

Microcapsules comprising an agglomeration of primary microcapsules, each individual primary microcapsule having a primary shell and the agglomeration being encapsulated by an outer shell, may be prepared by providing an aqueous mixture of a loading substance and a shell material, adjusting pH, temperature, concentration and/or mixing speed to form primary shells of shell material around the loading substance and cooling the aqueous mixture until the primary shells agglomerate and an outer shell of shell material forms around the agglomeration. Such microcapsules are useful for storing a substance and for delivering the substance to a desired environment.

FIELD OF THE INVENTION

This invention relates to microcapsules, methods of preparingmicrocapsules and to their use.

BACKGROUND OF THE INVENTION

Microcapsules are defined as small particles of solids, or droplets ofliquids, inside a thin coating of a shell material such as beeswax,starch, gelatine or polyacrylic acid. They are used, for example, toprepare liquids as free-flowing powders or compressed solids, toseparate reactive materials, to reduce toxicity, to protect againstoxidation and/or to control the rate of release of a substance such asan enzyme, a flavour, a nutrient, a drug, etc.

Over the past fifty years, the prior art has concentrated on so-called“single-core” microcapsules. However, one of the problems withsingle-core microcapsules is their susceptibility to rupture. Toincrease the strength of microcapsules, it is known in the art toincrease the thickness of the microcapsule wall. However, this leads toa reduction in the loading capacity of the microcapsule. Anotherapproach has been to create so-called “multi-core” microcapsules. Forexample, U.S. Pat. No. 5,780,056 discloses a “multi-core” microcapsulehaving gelatine as a shell material. These microcapsules are formed byspray cooling an aqueous emulsion of oil or carotenoid particles suchthat the gelatine hardens around “cores” of the oil or carotenoidparticles. Yoshida et al. (Chemical Abstract 1990:140735 or Japanesepatent publication JP 01-148338 published Jun. 9, 1989) discloses acomplex coacervation process for the manufacture of microcapsules inwhich an emulsion of gelatine and paraffin wax is added to an arabicrubber solution and then mixed with a surfactant to form “multi-core”microcapsules. Ijichi et al. (J. Chem. Eng. Jpn. (1997) 30(5):793-798)micoroencapsulated large droplets of biphenyl using a complexcoacervation process to form multi-layered mirocapsules. U.S. Pat. No.4,219,439 and 4,222,891 disclose “multi-nucleus”, oil-containingmicrocapsules having an average diameter of 3-20 μm with an oil dropletsize of 1-10 μm for use in pressure-sensitive copying papers and heatsensitive recording papers. While some improvement in the strength ofmicrocapsules may be realized by using methods such as these, thereremains a need for microcapsules having good rupture strength and goodoxidative barrier to the encapsulated substance, preferably inconjunction with high load volumes. Illustrative of this need is thecurrent lack of commercially available ‘multicore’ microcapsules.

SUMMARY OF THE INVENTION

There is provided a microcapsule comprising an agglomeration of primarymicrocapsules, each individual primary microcapsule having a primaryshell and the agglomeration being encapsulated by an outer shell. Thereis further provided a process for preparing microcapsules, the processcomprising:

-   (a) providing an aqueous mixture of a loading substance, a first    polymer component of shell material and a second polymer component    of shell material;-   (b) adjusting pH, temperature, concentration, mixing speed or a    combination thereof to form shell material comprising the first and    second polymer components, the shell material forming primary shells    around the loading substance;-   (c) cooling the aqueous mixture to a temperature above gel point of    the shell material until the primary shells form agglomerations;    and,-   (d) further cooling the aqueous mixture to form an outer shell of    shell material around the agglomerations.

There is still further provided a process for preparing microcapsules,the process comprising:

-   (a) providing an aqueous mixture of a first polymer component of    shell material;-   (b) dispersing a loading substance into the aqueous mixture;-   (c) then adding a second polymer component of shell material to the    aqueous mixture;-   (d) adjusting pH, temperature, concentration, mixing speed or a    combination thereof to form shell material comprising complex    coacervates of the first and second polymer components, the shell    material forming primary shells around the loading substance;-   (e) cooling the aqueous mixture to a temperature above gel point of    the shell material until the primary shells form agglomerations;    and,-   (f) further cooling the aqueous mixture to form an outer shell of    shell material around the agglomerations.

Microcapsules of the present invention may be used to contain a loadingsubstance for a variety of applications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an optical micrograph (400 ×) of encapsulated agglomerationsof microcapsules in accordance with the invention.

FIG. 2 is a second optical micrograph (400 ×) of encapsulatedagglomerations of microcapsules in accordance with the invention.

DETAILED DESCRIPTION

Composition:

The loading substance may be virtually any substance that is notentirely soluble in the aqueous mixture. Preferably, the loadingsubstance is a solid, a hydrophobic liquid, or a mixture of a solid anda hydrophobic liquid. The loading substance is more preferably ahydrophobic liquid, such as grease, oil or a mixture thereof. Typicaloils may be fish oils, vegetable oils, mineral oils, derivatives thereofor mixtures thereof.

The loading substance may comprise a purified or partially purified oilysubstance such as a fatty acid, a triglyceride or a mixture thereof.Omega-3 fatty acids, such as α-linolenic acid (18:3n3),octadecatetraenoic acid (18:4n3), eicosapentaenoic acid (20:5n3) (EPA)and docosahexaenoic acid (22:6n3) (DHA), and derivatives thereof andmixtures thereof, are preferred. Many types of derivatives are wellknown to one skilled in the art. Examples of suitable derivatives areesters, such as phytosterol esters, branched or unbranched C₁-C₃₀ alkylesters, branched or unbranched C₂-C₃₀ alkenyl esters or branched orunbranched C₃-C₃₀ cycloalkyl esters, in particular phytosterol estersand C₁-C₆ alkyl esters. Preferred sources of oils are oils derived fromaquatic organisms (e.g. anchovies, capelin, Atlantic cod, Atlanticherring, Atlantic mackerel, Atlantic menhaden, salmonids, sardines,shark, tuna, etc) and plants (e.g. flax, vegetables, algae, etc). Whilethe loading substance may or may not be a biologically active substance,the microcapsules of the present invention are particularly suited forbiologically active substances, for example, drugs, nutritionalsupplements, flavours or mixtures thereof. Particularly preferredloading substances include antioxidants, such as CoQ₁₀ and vitamin E.

The shell material may be any material that can form a microcapsulearound the loading substance of interest. The shell material typicallycomprises at least one polymer component. Examples of polymer componentsinclude, but are not limited to, gelatines, polyphosphate,polysaccharides and mixtures thereof. Preferred polymer components aregelatine A, gelatine B, polyphosphate, gum arabic, alginate, chitosan,carrageenan, pectin, carboxy-methylcellulose (CMC) or a mixture thereof.A particularly preferred form of gelatine type A has a Bloom strength of50-350, more preferably a Bloom strength of 275.

The shell material is preferably a two-component system made from amixture of different types of polymer components. More preferably, theshell material is a complex coacervate between two or more polymercomponents. Component A is preferably gelatine type A, although otherpolymers are also contemplated as component A. Component B is preferablygelatine type B, polyphosphate, gum arabic, alginate, chitosan,carrageenan, pectin, carboxymethyl-cellulose or a mixture thereof. Themolar ratio of component A:component B that is used depends on the typeof components but is typically from 1:5 to 15:1. For example, whengelatine type A and polyphosphate are used as components A and Brespectively, the molar ratio of component A:component B is preferably8:1 to 12:1; when gelatine type A and gelatine type B are used ascomponents A and B respectively, the molar ratio of componentA:component B is preferably 2:1 to 1:2; and when gelatine type A andalginate are used as components A and B respectively, the molar ratio ofcomponent A:component B is preferably 3:1 to 5:1.

Processing aids may be included in the shell material. Processing aidsmay be used for a variety of reasons. For example, they may be used topromote agglomeration of the primary microcapsules, control microcapsulesize and/or to act as an antioxidant. Antioxidant properties are usefulboth during the process (e.g. during coacervation and/or spray drying)and in the microcapsules after they are formed (i.e. to extendshelf-life, etc). Preferably a small number of processing aids thatperform a large number of functions is used. For example, ascorbic acidor a salt thereof may be used to promote agglomeration of the primarymicrocapsules, to control microcapsule size and to act as anantioxidant. The ascorbic acid or salt thereof is preferably used in anamount of about 100 ppm to about 10,000 ppm, more preferably about 1000ppm to about 5000 ppm. A salt of ascorbic acid, such as sodium orpotassium ascorbate, is particularly preferred in this capacity.

The structure of encapsulated agglomerations of microcapsules inaccordance with the present invention may be seen in FIGS. 1 and 2,which show that smaller (primary) microcapsules have agglomeratedtogether and that the agglomeration is surrounded by shell material toform a larger microcapsule. Each individual primary microcapsule has itsown distinct shell called the primary shell. Furthermore, any space thatthere may be between the smaller microcapsules is filled with more shellmaterial to hold and surround the smaller microcapsules therebyproviding an extremely strong outer shell of the larger microcapsule inaddition to the primary shell that forms the smaller microcapsuleswithin the larger microcapsule. In one sense, the encapsulatedagglomeration of microcapsules may be viewed as an agglomeration ofwalled bubbles suspended in a matrix of shell material, i.e. a“foam-like” structure. Such an encapsulated agglomeration ofmicrocapsules provides a stronger, more rupture-resistant structure thanis previously known in the art, in conjunction with achieving high loadsof loading substance.

The primary microcapsules (primary shells) typically have an averagediameter of about 40 nm to about 10 μm, more particularly from about 0.1μm to about 5 μm, even more particularly about 1 μm. The encapsulatedagglomerations (outer shells) may have an average diameter of from about1 μm to about 2000 μm, more typically from about 20 μm to about 1000 μm,more particularly from about 20 μm to about 100 μm, even moreparticularly from about 50 μm to about 100 μm.

The encapsulated agglomerations of microcapsules prepared by a processof the present invention typically have a combination of payload andstructural strength that are better than multi-core microcapsules of theprior art. For example, payloads of loading substance can be as high asabout 70% by weight in microcapsules of the present invention having anaverage size of about 50 μm for the outer shells and an average size ofabout 1 μm for the primary shells.

Process:

In the process for preparing microcapsules, an aqueous mixture of aloading substance, a first polymer component of the shell material and asecond polymer component of the shell material is formed. The aqueousmixture may be a mechanical mixture, a suspension or an emulsion. When aliquid loading material is used, particularly a hydrophobic liquid, theaqueous mixture is preferably an emulsion of the loading material andthe polymer components.

In a more preferred aspect, a first polymer component is provided inaqueous solution, preferably together with processing aids, such asantioxidants. A loading substance may then be dispersed into the aqueousmixture, for example, by using a homogenizer. If the loading substanceis a hydrophobic liquid, an emulsion is formed in which a fraction ofthe first polymer component begins to deposit around individual dropletsof loading substance to begin the formation of primary shells. If theloading substance is a solid particle, a suspension is formed in which afraction of the first polymer component begins to deposit aroundindividual particles to begin the formation of primary shells. At thispoint, another aqueous solution of a second polymer component may beadded to the aqueous mixture.

Droplets or particles of the loading substance in the aqueous mixturepreferably have an average diameter of less than 100 μm, more preferablyless than 50 μm, even more preferably less than 25 μm. Droplets orparticles of the loading substance having an average diameter less than10 μm or less than 5 μm or less than 3 μm or less than 1 μm may be used.Particle size may be measured using any typical equipment known in theart, for example, a Coulter™ LS230 Particle Size Analyzer, Miami, Fla.,USA.

The amount of the polymer components of the shell material provided inthe aqueous mixture is typically sufficient to form both the primaryshells and the outer shells of the encapsulated agglomeration ofmicrocapsules. Preferably, the loading substance is provided in anamount of from about 1% to about 15% by weight of the aqueous mixture,more preferably from about 3% to about 8% by weight, and even morepreferably about 6% by weight.

The pH, temperature, concentration, mixing speed or a combinationthereof is then adjusted to accelerate the formation of the primaryshells around the droplets or particles of the loading substance. Ifthere is more than one type of polymer component, complex coacervationwill occur between the components to form a coacervate, which furtherdeposits around the loading substance to form primary shells of shellmaterial. The pH adjustment depends on the type of shell material to beformed. For example, when gelatine type A is a polymer component, the pHmay be adjusted to a value from 3.5-5.0, preferably from 4.0-5.0. If thepH of the mixture starts in the desired range, then little or no pHadjustment is required. The initial temperature of the aqueous mixtureis preferably set to a value of from about 40° C. to about 60° C., morepreferably at about 50° C. Mixing is preferably adjusted so that thereis good mixing without breaking the microcapsules as they form.Particular mixing parameters depend on the type of equipment being used.Any of a variety of types of mixing equipment known in the art may beused. Particularly useful is an axial flow impeller, such as Lightnin™A310 or A510.

The aqueous mixture may then be cooled under controlled cooling rate andmixing parameters to permit agglomeration of the primary shells to formencapsulated agglomerations of primary shells. The encapsulatedagglomerations are discrete particles themselves. It is advantageous tocontrol the formation of the encapsulated agglomerations at atemperature above the gel point of the shell material, and to let excessshell material form a thicker outer shell. It is also possible at thisstage to add more polymer components, either of the same kind or adifferent kind, in order to thicken the outer shell and/or producemicrocapsules having primary and outer shells of different composition.The temperature is preferably lowered at a rate of 1° C./10 minutesuntil it reaches a temperature of from about 5° C. to about 10° C.,preferably about 5° C. The outer shell encapsulates the agglomeration ofprimary shells to form a rigid encapsulated agglomeration ofmicrocapsules.

At this stage, a cross-linker may be added to further increase therigidity of the microcapsules by cross-linking the shell material inboth the outer and primary shells and to make the shells insoluble inboth aqueous and oily media. Any suitable cross-linker may be used andthe choice of cross-linker depends somewhat on the choice of shellmaterial. Preferred cross-linkers are enzymatic cross-linkers (e.g.transglutaminase), aldehydes (e.g. formaldehyde or gluteraldehyde),tannic acid, alum or a mixture thereof. When the microcapsules are to beused to deliver a biologically active substance to an organism, thecross-linkers are preferably non-toxic or of sufficiently low toxicity.The amount of cross-linker used depends on the type of shell materialand may be adjusted to provide more or less structural rigidity asdesired. For example, when gelatine type A is used in the shellmaterial, the cross-linker may be conveniently used in an amount ofabout 1.0% to about 5.0%, preferably about 2.5%, by weight of thegelatine type A. In general, one skilled in the art may routinelydetermine the desired amount in any given case by simpleexperimentation.

Finally, the microcapsules may be washed with water and/or dried toprovide a free-flowing powder. Drying may be accomplished by a number ofmethods known in the art, such as freeze drying, drying with ethanol orspray drying. Spray drying is a particularly preferred method for dryingthe microcapsules. Spray drying techniques are disclosed in “SprayDrying Handbook”, K. Masters, 5^(th) edition, Longman ScientificTechnical UK, 1991, the disclosure of which is hereby incorporated byreference.

Uses:

The microcapsules produced by the process of the present invention maybe used to prepare liquids as free-flowing powders or compressed solids,to store a substance, to separate reactive substances, to reducetoxicity of a substance, to protect a substance against oxidation, todeliver a substance to a specified environment and/or to control therate of release of a substance. In particular, the microcapsules may beused to deliver a biologically active substance to an organism fornutritional or medical purposes. The biologically active substance maybe, for example, a nutritional supplement, a flavour, a drug and/or anenzyme. The organism is preferably a mammal, more preferably a human.Microcapsules containing the biologically active substance may beincluded, for example, in foods or beverages or in drug deliverysystems. Use of the microcapsules of the present invention forformulating a nutritional supplement into human food is particularlypreferred.

Microcapsules of the present invention have good rupture strength tohelp reduce or prevent breaking of the microcapsules duringincorporation into food or other formulations. Furthermore, themicrocapsule's shells are insoluble in both aqueous and oily media, andhelp reduce or prevent oxidation and/or deterioration of the loadingsubstance during preparation of the microcapsules, during long-termstorage, and/or during incorporation of the microcapsules into aformulation vehicle, for example, into foods, beverages, nutraceuticalformulations or pharmaceutical formulations.

EXAMPLES Example 1

54.5 grams gelatine 275 Bloom type A (isoelectric point of about 9) wasmixed with 600 grams of deionized water containing 0.5% sodium ascorbateunder agitation at 50° C. until completely dissolved. 5.45 grams ofsodium polyphosphate was dissolved in 104 grams of deionized watercontaining 0.5% sodium ascorbate. 90 grams of a fish oil concentratecontaining 30% eicosapentaenoic acid ethyl ester (EPA) and 20%docosahexaenoic acid ethyl ester (DHA) (available from Ocean NutritionCanada Ltd.) was dispersed with 1.0% of an antioxidant (blend of naturalflavour, tocopherols and citric acid available as Duralox™ from Kalsec™)into the gelatine solution with a high speed Polytron™ homogenizer. Anoil-in-water emulsion was formed. The oil droplet size had a narrowdistribution with an average size of about 1 μm measured by Coulter™LS230 Particle Size Analyzer. The emulsion was diluted with 700 grams ofdeionized water containing 0.5% sodium ascorbate at 50° C. The sodiumpolyphosphate solution was then added into the emulsion and mixed with aLightning agitator at 600 rpm. The pH was then adjusted to 4.5 with a10% aqueous acetic acid solution. During pH adjustment and the coolingstep that followed pH adjustment, a coacervate formed from the gelatineand polyphosphate coated onto the oil droplets to form primarymicrocapsules. Cooling was carried out to above the gel point of thegelatine and polyphosphate and the primary microcapsules started toagglomerate to form lumps under agitation. Upon further cooling of themixture, polymer remaining in the aqueous phase further coated the lumpsof primary microcapsules to form an encapsulated agglomeration ofmicrocapsules having an outer shell and having an average size of 50 μm.Once the temperature had been cooled to 5° C., 2.7 grams of 50%gluteraldehyde was added into the mixture to further strengthen theshell. The mixture was then warmed to room temperature and kept stirringfor 12 hours. Finally, the microcapsule suspension washed with water.The washed suspension was then spray dried to obtain a free-flowingpowder. A payload of 60% was obtained.

Example 2

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that 0.25% sodium ascorbate wasused. A payload of 60% was obtained.

Example 3

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that no ascorbate was used. Apayload of 60% was obtained.

Example 4

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that 105 grams of fish oilconcentrate was used and a payload of 70% was obtained.

Example 5

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that it was applied to triglyceride(TG) fish oil (available from Ocean Nutrition Canada Ltd.) rather thanethyl ester fish oil.

Example 6

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that gelatine (type A) and gumarabic were used as polymer components of the shell material.

Example 7

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that 150 Bloom gelatine (type A) andpolyphosphate were used as polymer components of the shell material and105 grams of fish oil concentrate was used to obtain a payload of 70%.

Example 8

Encapsulated agglomerations of microcapsules were formed in accordancewith the method of Example 1 except that transglutaminase was used tocross-link the shell material.

Example 9 Evaluation of Microcapsules

The microcapsules of Examples 1-8 were evaluated for mechanicalstrength, encapsulated oil quality and oxidative stability.

Microcapsule shell strength was evaluated by centrifuging a given amountof the prepared microcapsule powders from each of the Examples 1-8 at34,541 g at 25° C. for 30 minutes in a Sorvall™ Super T-21 centrifuge.The original and the centrifuged powders were washed with hexane toextract oil released from the microcapsules due to shell breakage undercentrifuge force. The ratio of percent free oil of the centrifugedpowders to that of the original powders is used as an indicator of theshell strength. The lower the ratio, the stronger is the microcapsule'sshell.

Oil quality in microcapsules was evaluated by crushing the shells of theprepared microcapsule powders from each of Examples 1-8 with a grinder.The encapsulated oil was then extracted with hexane. Peroxide Value (PV)was analyzed with American Oil Chemist Society Method (AOCS OfficialMethod Cd 8-53: Peroxide value). A high PV indicates a higherconcentration of primary oxidation products in the encapsulated oil.

Accelerated oxidative stability was evaluated by placing the preparedmicrocapsule powders from each of Examples 1-8 in an oxygen bomb(Oxipres™, MIKROLAB AARHUS A/S, Denmark) with an initial oxygen pressureof 5 bar at a constant temperature of 65° C. When the encapsulated fishoil started to oxidize, the oxygen pressure dropped. The time at whichthe oxygen pressure started to drop is called Induction Period. A longerInduction Period means that the contents of the microcapsules are betterprotected towards oxidation.

Results are shown in Table 1. The results indicate that the agglomeratedmicrocapsules prepared in accordance with the present invention haveexcellent strength and resistance to oxidation of the encapsulatedloading substance.

TABLE 1 induct free load ascorbate period PV oil run # (%) (%) (hr)value ratio notes 1 60 0.50 38 3.0 2.0 2 60 0.25 34 4.1 1.5 3 60 0.0 267.8 1.5 4 70 0.50 38 3.2 1.7 5 60 0.50 37 0.28 3.0 TG oil 6 60 0.50 303.4 1.5 gum arabic 7 70 0.50 38 4.4 2.2 150 bloom gelatin 8 60 0.50 333.2 1.1 enzymatic cross linking

Other advantages which are obvious and which are inherent to theinvention will be evident to one skilled in the art. It will beunderstood that certain features and sub-combinations are of utility andmay be employed without reference to other features andsub-combinations. This is contemplated by and is within the scope of theclaims. Since many possible embodiments may be made of the inventionwithout departing from the scope thereof, it is to be understood thatall matter herein set forth or shown in the accompanying drawings is tobe interpreted as illustrative and not in a limiting sense.

1. A microcapsule comprising an agglomeration of primary microcapsules,each individual primary microcapsule having a primary shell and theagglomeration being encapsulated by an outer shell.
 2. The microcapsuleaccording to claim 1, wherein the outer shell is a matrix of shellmaterial that surrounds the agglomeration to form a foam-like structure.3. The microcapsule according to claim 2, wherein the shell materialcomprises gelatine, polyphosphate, polysaccharide, or a mixture thereof.4. The microcapsule according to claim 2, wherein the shell materialcomprises gelatine type A, gelatine type B, polyphosphate, gum arabic,alginate, chitosan, carrageenan, pectin, carboxymethylcellulose or amixture thereof.
 5. The microcapsule according to claim 2, wherein theshell material is a complex coacervate.
 6. The microcapsule according toclaim 2, wherein the shell material is a complex coacervate betweengelatine A and one or more of a polymer component selected from thegroup consisting of gelatine type B, polyphosphate, gum arabic,alginate, chitosan, carrageenan, pectin and carboxymethylcellulose. 7.The microcapsule according to claim 2, wherein the shell material is acomplex coacervate between gelatine A and polyphosphate.
 8. Themicrocapsule according to claim 3, wherein the shell material furthercomprises an antioxidant.
 9. The microcapsule according to claim 8,wherein the antioxidant is ascorbic acid or a salt thereof.
 10. Themicrocapsule according to claim 8, wherein the antioxidant is sodiumascorbate.
 11. The microcapsule according to claim 2, wherein the outershell has an average diameter of from about 1 μm to about 2000 μm. 12.The microcapsule according to claim 2, wherein the outer shell has anaverage diameter of from about 20 μm to about 1000 μm.
 13. Themicrocapsule according to claim 2, wherein the outer shell has anaverage diameter of from about 20 μm to about 100 μm.
 14. Themicrocapsule according to claim 2, wherein the outer shell has anaverage diameter of from about 50 μm to about 100 μm.
 15. Themicrocapsule according to claim 2, wherein the primary shells have anaverage diameter of from about 40 nm to about 10 μm.
 16. Themicrocapsule according to claim 2, wherein the primary shells have anaverage diameter of from about 0.1 μm to about 5 μm.
 17. Themicrocapsule according to claim 2, wherein the primary shells have anaverage diameter of about 1 μm.
 18. The microcapsule according to claim2, having a payload of loading substance of up to about 70% by weight.19. The microcapsule according to claim 2, wherein the loading substanceis a solid, a liquid or a mixture thereof.
 20. The microcapsuleaccording to claim 2, wherein the loading substance is grease, oil or amixture thereof.
 21. The microcapsule according to claim 2, wherein theloading substance is a biologically active substance.
 22. Themicrocapsule according to claim 2, wherein the loading substance is anutritional supplement.
 23. The microcapsule according to claim 2,wherein the loading substance is a triglyceride, an omega-3 fatty acid,an ester of an omega-3 fatty acid and/or mixtures thereof.
 24. Themicrocapsule according to claim 2, wherein the loading substance is aphytosterol ester of docosahexaenoic acid and/or eicosapentaenoic acid,a C₁-C₆ alkyl ester of docosahexaenoic acid and/or eicosapentaenoicacid, and/or a mixture thereof.
 25. A process for preparingmicrocapsules, the process comprising: (a) providing an aqueous mixtureof a loading substance, a first polymer component of shell material anda second polymer component of shell material; (b) adjusting pH,temperature, concentration, mixing speed or a combination thereof toform shell material comprising the first and second polymer components,the shell material forming primary shells around the loading substance;(c) cooling the aqueous mixture to a temperature above gel point of theshell material until the primary shells form agglomerations; and, (d)further cooling the aqueous mixture to form an outer shell of shellmaterial around the agglomerations.
 26. The process according to claim25, wherein the first polymer component is gelatine type A.
 27. Theprocess according to claim 25, wherein the second polymer component isgelatine type B, polyphosphate, gum arabic, alginate, chitosan,carrageenan, pectin, carboxymethylcellulose or a mixture thereof. 28.The process according to claim 25, wherein the second polymer componentis polyphosphate.
 29. The process according to claim 25, wherein theloading substance is grease, oil or a mixture thereof and is dispersedas an emulsion in the aqueous mixture.
 30. The process according toclaim 25, wherein the loading substance is a triglyceride, an omega-3fatty acid, an ester of an omega-3 fatty acid and/or mixtures thereof.31. The process according to claim 25, wherein the loading substance isprovided in an amount of from about 1% to about 15% by weight of theaqueous mixture.
 32. The process according to claim 25, wherein anantioxidant is added to the aqueous mixture in part (a).
 33. The processaccording to claim 25, wherein ascorbic acid or a salt thereof is addedto the aqueous mixture in part (a).
 34. The process according to claim25, wherein sodium ascorbate is added to the aqueous mixture in part(a).
 35. The process according to claim 25, wherein the pH is adjustedto a value from 3.5-5.0.
 36. The process according claim 25, wherein thepH is adjusted to a value from 4.0-5.0.
 37. The process according toclaim 25, wherein the temperature is initially from about 40° C. toabout 60° C.
 38. The process according to claim 25, wherein thetemperature is initially about 50° C.
 39. The process according to claim25, wherein the mixture is cooled at a rate of 1° C./10 minutes.
 40. Theprocess according to claim 25, wherein the mixture is cooled until itreaches a temperature of from about 5° C. to about 10° C.
 41. Theprocess according to claim 25, wherein the mixture is cooled until itreaches a temperature of about 5° C.
 42. The process according to claim25, further comprising step (g) adding a cross-linker to cross-link theshell material.
 43. The process according to claim 42, wherein thecross-linker is an enzymatic cross-linker, an aldehyde, tannic acid,alum or a mixture thereof.
 44. The process according to claim 42,wherein the cross-linker is gluteraldehyde.
 45. The process according toclaim 42, wherein the cross-linker is transglutaminase.
 46. The processaccording to claim 25, further comprising step of drying themicrocapsules.
 47. A process for preparing microcapsules, the processcomprising: (a) providing an aqueous mixture of a first polymercomponent of shell material; (b) dispersing a loading substance into theaqueous mixture; (c) then adding a second polymer component of shellmaterial to the aqueous mixture; (d) adjusting pH, temperature,concentration, mixing speed or a combination thereof to form shellmaterial comprising complex coacervates of the first and second polymercomponents, the shell material forming primary shells around the loadingsubstance; (e) cooling the aqueous mixture to a temperature above gelpoint of the shell material until the primary shells formagglomerations; and, (f) further cooling the aqueous mixture to form anouter shell of shell material around the agglomerations.
 48. The processaccording to claim 47, wherein the first polymer component is gelatinetype A.
 49. The process according to claim 47, wherein the secondpolymer component is gelatine type B, polyphosphate, gum arabic,alginate, chitosan, carrageenan, pectin, carboxymethylcellulose or amixture thereof.
 50. The process according to claim 47, wherein thesecond polymer component is polyphosphate.
 51. The process according toclaim 47, further comprising adding more polymer components to theaqueous mixture in part (e).
 52. The process according to claim 47,wherein the loading substance is grease, oil or a mixture thereof and isdispersed as an emulsion in the aqueous mixture.
 53. The processaccording to claim 47, wherein the loading substance is a triglyceride,an omega-3 fatty acid, an ester of an omega-3 fatty acid and/or mixturesthereof.
 54. The process according to claim 47, wherein the loadingsubstance is provided in an amount of from about 1% to about 15% byweight of the aqueous mixture.
 55. The process according to claim 47,wherein an antioxidant is added to the aqueous mixture in part (a). 56.The process according to claim 47, wherein ascorbic acid or a saltthereof is added to the aqueous mixture in part (a).
 57. The processaccording to claim 47, wherein sodium ascorbate is added to the aqueousmixture in part (a).
 58. The process according to claim 47, wherein thepH is adjusted to a value from 3.5-5.0.
 59. The process according claim47, wherein the pH is adjusted to a value from 4.0-5.0.
 60. The processaccording to claim 47, wherein the temperature is initially from about40° C. to about 60° C.
 61. The process according to claim 47, whereinthe temperature is initially about 50° C.
 62. The process according toclaim 47, wherein the mixture is cooled at a rate of 1° C./10 minutes.63. The process according to claim 47, wherein the mixture is cooleduntil it reaches a temperature of from about 5° C. to about 10° C. 64.The process according to claim 47, wherein the mixture is cooled untilit reaches a temperature of about 5° C.
 65. The process according toclaim 47, further comprising step (g) adding a cross-linker tocross-link the shell material.
 66. The process according to claim 65,wherein the cross-linker is an enzymatic cross-linker, an aldehyde,tannic acid, alum or a mixture thereof.
 67. The process according toclaim 65, wherein the cross-linker is gluteraldehyde.
 68. The processaccording to claim 65, wherein the cross-linker is transglutaminase. 69.The process according to claim 47, further comprising step of drying themicrocapsules.
 70. Microcapsules prepared by a process according toclaim
 25. 71. Microcapsules prepared by a process according to claim 47.